For medical devices, in particular for operating tables, remote controls are available as wireless operating devices, with the aid of which the respective device can be operated from various positions and at a certain distance from a receiver unit of the device for receiving the signals from the remote control. Such remote controls make convenient use of at least some of the operating functions of the medical device or of the operating table possible. Such operating devices are operated by batteries or rechargeable batteries in the prior art. In order to ensure ease of use of such a remote control, it is recommended to use rechargeable batteries, as a result of which the remote control can be used as the operating unit throughout subsequent treatment once the rechargeable batteries have been charged or recharged.
In addition, the use of special rechargeable batteries makes it possible to provide a large quantity of energy for operation of the remote control in the case of a relatively small physical size which is matched to the design-related conditions of the remote control. In order to charge the rechargeable batteries, a connection to a further energy source, in particular to a suitable switched-mode power supply or to a charger, needs to be produced. For this purpose, both arrangements with a DC connection between the charger and the rechargeable battery and without a DC connection between the charger and the rechargeable battery are known in the prior art. In the case of the known arrangements in which there is no DC connection between the remote control and the energy source (i.e. in the case of DC isolation), the energy transmission generally takes place inductively between a charging station or base station and the remote control. The charging station or the base station is in this case the source device and the remote control is the target device.
FIG. 1 illustrates a known arrangement 10 for the inductive transmission of energy. The arrangement 10 in this case comprises a source device 12 and a target device 14. The source device 12 comprises an energy source 16, which is in the form of an AC source and generates an AC voltage. In addition, the source device 12 comprises a coil 18 on the source-device side which acts as a primary coil 18 for energy or data transmission to the target device 14. The target device 14 comprises a coil 20 on the target-device side which acts as a secondary coil 20 and is electrically connected to a charging circuit 22, which is illustrated as a load resistor. The energy source 16 of the source device 12 is electrically connected to the primary coil 18 on the source-device side, with the result that the energy source 16 brings about an alternating current flow through the coil 18, as a result of which the coil 18 generates a magnetic field which changes over time (alternating magnetic field). The secondary coil 20 on the target-device side is located in the magnetic field induced by the primary coil 18 if the target device 14 is located in a charging and/or data transmission position. A voltage is induced in the secondary coil 20 by means of the alternating magnetic field, and, as a result of this voltage, a current flow through the charging circuit 22, which is illustrated as a load resistor, is possible, with the result that the energy transmitted from the energy source 16 via the coils 18, 20 is supplied to this charging circuit 22. As an alternative or in addition to the charging circuit 22, an evaluation circuit for determining data transmitted via the arrangement shown in FIG. 1 can be provided.
FIG. 2 illustrates an arrangement 24 for transmitting energy between a source device 26 and a target device 28 similar to the arrangement 10 shown in FIG. 1. Identical elements have the same reference symbols. In contrast to the arrangement 10 shown in FIG. 1, the circuit of the source device 26 and the circuit of the target device 28 each contain a capacitor 30, 32. A series resonant circuit is formed by the arrangement of the capacitor 30 in the circuit of the source device 26 and a parallel resonant circuit is formed by the capacitor 32 in the secondary circuit. Resonant coupling takes place between the source device 26 and the target device 28 by means of these resonant circuits, and this results in a relatively high efficiency in the transmission of energy from the primary circuit to the secondary circuit or from the source device 26 to the target device 28. In the arrangement 24 shown in FIG. 2, a magnetic field is induced by the primary coil 18. The primary coil 18 and the capacitor 30 form a primary circuit which is tuned to resonance. The magnetic field induced by the primary coil 18 passes through the secondary coil 20, which is part of the secondary resonant circuit. However, in practice it is difficult to match the resonant frequencies of the primary-side resonant circuit and of the secondary-side resonant circuit to one another since the resonance conditions change depending on the state of charge of the rechargeable batteries or depending on the resistance value of the load resistor 22, which changes over the charging cycle.
In order to match the resonant frequency, various measures are conceivable both on the primary side and on the secondary side. For example, a suitable frequency of the energy source 16 can be selected, with it being possible for the frequency to be preset, set in a predetermined frequency range, regulated or corrected. Furthermore, suitable design measures, in particular mechanical and electronic measures, can be provided in order to maintain the resonance conditions over a relatively long charging cycle. In particular, maintenance of the resonance condition can be achieved or at least assisted by a suitable selection of components. In addition, resonance adjustment can be achieved by changing the capacitance of at least one of the capacitors 30, 32 or the inductance of at least one of the coils 18, 20. However, this is associated with a relatively high level complexity. Overall, maintenance of the resonance conditions in the primary and/or secondary circuit is relatively complex.
FIG. 3 illustrates an arrangement 34 for transmitting energy between a source device 36 and a target device 38 similar to the arrangement 10 shown in FIG. 1. In contrast to the arrangement 10 shown in FIG. 1, the primary coil 18 is arranged around a first iron core segment 40 and the secondary coil 20 is arranged around a second iron core segment 42. The iron core segments 40, 42 have a gap 44 on their mutually facing end sides in a charging and/or data transmission position. The gap 44 is in particular formed by the respectively closed housings of the source device 36 and of the target device 38 and/or by an additional air gap. The lines of force emerging from one of the end sides, which are remote from one another, of the magnet core segments 40, 42 enter the opposite remote end side and close the magnetic circuit with the magnet core segments 40, 42 and with the gap 44.
FIG. 4 shows an arrangement 46 similar to the arrangement 34 shown in FIG. 3, with, both in the case of the source device 48 and in the case of the target device 50, magnet core segments 52, 54 being inserted which are u-shaped and are arranged in a data and/or energy transmission position in such a way that in each case both end faces of the magnet core segments 52, 54 are opposite one another and are arranged at a distance from one another in such a way that in each case a gap 56, 58 similar to the gap 44 in the arrangement 34 is provided between these end sides.
FIG. 5 illustrates an arrangement 60 similar to the arrangement 46 shown in FIG. 4, with in each case one capacitor 30, 32 being provided in the circuit of the source device 62 and in the circuit of the target device 64 so as to form resonant circuits in the same way as already described in connection with FIG. 2.
In general, the housings of the source devices and of the target devices are made from electrically insulating material which does not weaken electromagnetic fields or weakens them only to a small extent. As a result of the minimum thicknesses required for the housing walls, in particular for the electrical insulation and mechanical strength of the housing of the source device and of the target device, the gap or gaps has or have a minimum gap width in the known embodiments shown which substantially influences the properties of the magnetic circuit. The gap width is critical for the magnetic field strength in the magnetic circuit, formed by the magnet core segments, of the arrangement shown in FIGS. 1 to 5.
The document DE 38 10 702 C2 has disclosed an arrangement in which a frequency correction of an energy source is carried out. For this purpose, in this arrangement the phase relationship between the current and the voltage in the primary circuit is determined and regulated to a preset value.
The document DE 198 37 675 A1 has disclosed a charging apparatus in which a power oscillator is provided in a primary part of an inductive coupler for the inductive transmission of charging energy. A switching apparatus for alternately drawing power for charging the rechargeable battery is provided in the secondary part.
The document DE 601 02 613 T2 has disclosed an arrangement in which the transmission power of the energy output by a transponder read apparatus is set. In this case, a series resonant circuit is provided in the primary-side or transmitter-side circuit for providing the transmission power. Up-to-date information on the magnetic coupling between a transponder and the read apparatus is detected. The resonant circuit has a variable capacitance, by means of which the resonant circuit can be tuned.